The invention pertains to a method for controlling a pressure in a high-pressure region of an injection system in an internal combustion engine and to an arrangement for implementing the presented method.
In internal combustion engines, injection systems are used to deliver fuel into the combustion chambers. The phrase “common-rail injection”, also called “accumulator injection”, is used to refer to a known injection system.
In a common-rail injection system, a high-pressure pump conveys fuel from a low-pressure region to a pressure accumulator, the so-called rail. The inlet cross section is typically controlled by a suction throttle. Injectors, which inject the fuel into the combustion chambers, i.e., the cylinders, are connected to the rail.
It is necessary to keep the pressure in the rail at a certain level in order to guarantee good combustion quality. For this purpose, a pressure control system is provided. This comprises, for example, a pressure controller, the suction throttle together with the high-pressure pump, and the rail. The pressure in the rail is thus the controlled variable. The measured pressure values are typically converted by way of a filter into an actual rail pressure, which is then compared with a nominal rail pressure. The deviation resulting from the comparison is converted by the pressure controller into a control input for the suction throttle. The pressure controller, the high-pressure pump with suction throttle, and the rail form the high-pressure control circuit.
A high-pressure control circuit is known in which the high fuel pressure is controlled by means of the suction throttle. The fuel is conveyed in this case by a single high-pressure pump.
A method for controlling the high fuel pressure is also known which again uses a suction throttle, in this case in a common-rail system with separate rails.
DE 103 42 130 A1 describes a method for operating an internal combustion engine with direct fuel injection. Here the fuel pressure in the fuel accumulator or rail is detected, and the length of the injection time is calculated on the basis of the detected value.
Injection systems are also known in which more than one type of fuel is burned. Injection systems in which two different fuels are used are called “dual-fuel injection systems”. In a dual-fuel injection system, both diesel fuel and gasoline can be injected into the combustion chamber of the engine.